Systems for controlling output torque of an internal combustion engine are known and one such system is described in U.S. Pat. No. 5,738,606 to Bellinger which is assigned to the assignee of the present invention, and the contents of which are incorporated herein by reference. One aspect of the Bellinger system is directed to control strategies for limiting engine output torque to the lowest value of the maximum input torque capacities of any of a number of drivetrain components. As a result, engine output torque is limited to the maximum input torque capacity of the weakest of the drivetrain components, thereby protecting all drivetrain components from excessive forces resulting from applied engine output torque.
Under certain vehicle operating conditions, the engine may also possesses substantial engine inertial torque which, if not properly accounted for, may also exceed the maximum input torque capacities of one or more of the drivetrain components. Thus, while systems such as that described in the '606 Bellinger reference may protect drivetrain components from excessive applied engine torque, no systems are known to exist that employ control strategies for protecting one or more of the drivetrain components from excessive engine inertial torque.
As an example of one vehicle operating condition wherein excessive engine inertial torque may damage drivetrain components, consider a tractor-trailer combination backing up to a loading dock in a low gear. If the vehicle operator errs and runs the back of the trailer into the dock, the wheels (as well as the various drivetrain components such as one or more transmissions, tailshaft, drive axle, clutch, etc.) stop rotating, yet the engine still possesses inertia. These rotational inertial forces possessed by the engine are accordingly transferred from the engine output drive shaft directly to the now locked drivetrain. These inertial forces may be substantial and could exceed the maximum input torque capacities of any one or more of the drivetrain components, thus resulting in excessive wear and/or drivetrain damage.
What is therefore needed is a system for protecting drivetrain components from excessive engine inertial torque. Such a system should ideally be operable to determine conditions wherein engine inertial torque is applied to the drivetrain, and implement a control strategy whereby the one or more drivetrain components are protected under conditions wherein the engine inertial torque may be excessive.